[PATCH v2] drm/i915: Don't disable interrupts independently of the lock

[Chris Wilson]

Quoting Sebastian Andrzej Siewior (2019-10-17 09:40:01)
> The locks (active.lock and rq->lock) need to be taken with disabled
> interrupts. This is done in i915_request_retire() by disabling the
> interrupts independently of the locks itself.
> While local_irq_disable()+spin_lock() equals spin_lock_irq() on vanilla
> it does not on PREEMPT_RT.
> Chris Wilson confirmed that local_irq_disable() was just introduced as
> an optimisation to avoid enabling/disabling interrupts during
> lock/unlock combo.
> 
> Enable/disable interrupts as part of the locking instruction.
> 
> Cc: Chris Wilson <chris at chris-wilson.co.uk>
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy at linutronix.de>
Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
-Chris